简单的if语句

$if [ 1 -eq 1 ]; then echo "Matched!"; fi
Matched!

“-eq”表示等于（equal to）。

不等于使用 "-ne"

$if [ 0 -ne 1 ]; then echo "Matched!"; fi
Matched!

if else语句

$if [ 1 -ne 1 ]; then echo "Matched!"; else echo "Not Matched!"; fi
Not Matched!

在Bash Shell脚本中使用if语句

$echo '#!/bin/bash' > myscript.sh
$echo 'if [ 1 -eq 1 ]; then echo "Matched!"; fi' >> myscript.sh 
$chmod +x myscript.sh 
$./myscript.sh 
Matched!
$

elif 语句

#!/bin/bash
if [ 0 -eq 1 ]; then 
  echo '0=1'
else
  if [ 0 -eq 2 ]; then
    echo '0=2'
  else
    echo '0!=2'
  fi
fi

可以改写成：

#!/bin/bash
if [ 0 -eq 1 ]; then
  echo '0=1'
elif [ 0 -eq 2 ]; then
  echo '0=2'
else
  echo '0!=2'
fi